[12p-B508-1~12] 3.5 Laser system and materials

▲ [12p-B508-6] 13 MW peak power second harmonic generation in doughnut mode Nd:YAG/Cr⁴⁺:YAG microchip laser

〇Hwan Hong LIM¹, Takunori Taira^1,2 (1.IMS, 2.RIKEN)

Keywords:Microchip laser with unstable cavity, Doughnut beam, Second harmonic generation

Microchip lasers are enlarging their application field with brightness scaling, such as laser ignition, remote laser induced breakdown spectroscopy (LIBS), high power THz generation, and so on. However, poor beam patterns of enlarged laser modes for energy scaling make further brightness scaling difficult because of pulse broadening and beam quality (M²) degradation. As a solution, we introduce an unstable resonator because 1) it is suitable to enlarge mode volume for energy scaling as keeping the beam pattern in doughnut shape and 2) the doughnut beam can be well focused as an Airy disk, which is good for high brightness. As a result, 26 MW peak power doughnut beam was demonstrated using a microchip laser with unstable resonator. In addition, the wavelength of 1064 nm was frequency doubled by second harmonic generation (SHG) using an LBO crystal. An SH peak power of 13 MW was achieved at a conversion efficiency of 50%. In a conclusion, a stable 13 MW peak power green doughnut beam laser was demonstrated by SHG of a Nd:YAG/Cr⁴⁺:YAG ceramic microchip laser with unstable resonator.